Power hammer



A. W. MALL POWER HAMMER Jan. 2, 1940.

5 Sheets-Shet 1 Filed June 15, 1937 I 47 27 %zz;-m 262/1 Jan. 2, 1940. w MAL-L 2,185,471

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POWER HAMMER Fild June 15, 1937 5 Sheets-5heet 4 9&5 1

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POWER HAMMER Filed June 15; 1937 5 Sheets-Sheet 5 A. w. MALL 2,185,471

Patented Jam 2, 1940 new are PoWEa HAMMER Arthur William Mall, Chicago, Ill. Application June 15, 1937, Serial No. 148,361

13 Claims.

My invention relates to improvements in power hammers and similar mechanisms.

My invention relates more particularly to a power hammer or similar mechanism adapted to be driven by means of a flexible shaft drive.

Power hammers of the type to which I refer havein' the past been driven by means of electric motors or by compressed air and are principally used for impacting purposes such as chipping, drilling,- riveting or tamping broken stone or similar ballast by means of a chisel, drill, rivet set, tamper bar or the like, to one end of which the striking member such as the hammer, piston, or power hammer imparts its blow. The principal object of the present invention is to provide an improved mechanical power hammer or similanunit capable of being driven ,by a flexible drive shaft froma remotely positi'oned source of power.

A further object of the present invention is to provide in a power hammer of the'type described a roller cam means for operating the piston back againstthe top of the cylinder head to compress the same, whereby the hammer blow the direct drive to the cam. H y A further object of the present invention is to provide an improved construction of power hammer whereby the cylindrical housing and associated parts are capable of independent removal' for repair or renewal.

"A further object of the present invention is to provide in connection withthe reciprocating piston improved cushioning means for the bottom of the piston-stroke. v

A further object of'the invention is to provide in connection with the reciprocating lever driven by the roller cam and adjustable shock absorber means capable of. yieldingly permitting the lever to 'becarried' downwardly by the piston in contact with a shoulder of the piston.

' A further object is toso construct the drive and associated parts that the power hammer may be easily assembled to or disassembled from a flexible'shaft fo-r'drivingthe same.

While-the prior'art' discloses a great many air driven power hammers and some electrically driven power hammers, it has. been found that these power hammers contain many objection- "--=able features:v The air'hammersin commercial useat the present timea're highly inefiicient in view'of the fact that air driven mechanisms of all types are known to have an efficiency ofnot over-15%:-. The'electrically operated power hammers are ordinarily: constructed with a motor is caused by the force of the 'pistoninstead of built into a housing adjacent the handle of the hammer, thereby causing additional expense for a motor housing and associated parts and also providing a device that is clumsy and bulky to handle and one which soon tires the average '5 worker. Furthermore, it is obvious that due to the terrific pounding which the motor is subjected to by reason of the action of the chipper, hammer or other work tool, the motor will quickly wear out or become broken. All of these 10 objectionable features are eliminated in the simple, light and compact power hammer which Ihave devised.

Other objects and advantages will be more easily understood from the following description, 15'

wherein reference is had to the accompanying five sheets of drawings, upon which Fig. 1 is a side elevational View of my improved power hammer showing a work tool attached' thereto in a driving relation;

Fig. 2 is a front elevational View of the manner inwhich the flexible drive for the same extends from the side thereof;

Fig. 3 is a vertical sectional view through the cylinder housing and associated parts;

Fig. 4 is a bottom fragmentary view taken generally on the lines d-dof Fig. 3 showing the adjustment for the operating lever recoil spring;

Fig. 5 isa vertical sectional view taken generally on the lines Ei--Ei'of Fig. 1 and showing the drive connection between the flexible shaft and the operating lever;

Fig. 6 is 'a plan sectional view through the housing, the operating lever and associated parts, taken generallyon the line 6-8 of Fig. 1;

Fig. '7 is an elevational View of the reciproeating piston; I

Fig. 8 is an elevational view of the forked operating lever, and

Fig. 9 is a side elevational View of the removable cylinder in which the operating piston operates. I

In the embodiment of my invention which I have chosen to illustrate, I provide generally the handle I!) connected between the cylinder housing I2 and the mechanism housing It.

To the side of the mechanism housing M I attach the housing [6 to which the housing It for the flexible shaft may be connected. The holder 20 provided with the right angle handle 22 is placed in the bottom of the cylinder housing 12 and may have connected thereto a work tool such as the chipper C shown in Fig. 1.

Referring now to Fig. 3, it can be seen that the handle member l0 may be in the form of a tubular member that has its. ends flattened. One end of the member I6 is connected by means of the bolt 24 to an upright flange 26 on the housing I4 and the other end is bent at right angles and has a ledge portion 28 that is fastened on the top of the cylinder cap 30 by means of a bolt member 32'. The housing I2 and the housing I4 which are formed integral, may have a pair of separated chambers 32 and 34. The chamber 32 may be formed with vertical cylindrical walls and a flat upper edge 36. The cylinder 33 within which the work piston operates is adapted to be closely fitted in the bore 3| in the cylinder housing I2, having its upper edge 38 flush with the top of the cylinder housing I 2 and having a shoulder 40 adapted to engage against the lower edge 42 of the housing I2. The cylinder may be formed with a vertical bore 44 terminating adjacent its upper end in an enlarged screw-threaded opening 46. The cylinder cap 39 is formed with a downwardly depending threaded plug portion 48 that is adapted to screwthreadedly engage the opening 46. The cap is further provided with a cylindrical flange 56 surrounding the plug 48 so that when the cap is screwed into position within the cylinder 33, the shoulder 56 is adapted to rest against the upper edges 36 and 38 of the housing I2 and the cylinder 33. The cylinder 39 may have a tapered bore 52 extending inwardly and connecting with a reduced bore 54 adjacent the lower end of the same. The bore 54 may extend downwardly for a distance, terminating in an inwardly directed and horizontal wall 56 where it connects with a further reduced bore 58. The cylinder is also provided with a generally rectangularly shaped opening 69 adjacent one side of the same to permit the introduction of an operating lever as will presently be apparent.

I provide a tool retainer bushing 62 adapted to be fixedly held in the bore 58 at the lower end of the cylinder 33. I also provide a hammer head bumper 64 preferably made of a molded synthetic rubber compound positioned about the bushing 62 and generally upon the set 56 in the bore 54. With the construction as thus described and shown, the end 26a of the tool retainer 26 will extend upwardly a short distance above the bushing 62 and the bumper 64. The reciprocating piston 66 may be formed with an upper cylindrical portion 68, a shank 69 and a lower cylindrical portion Ill. The portion 68 is adapted to be guided in its reciprocal motion in the bore 44 of the cylinder 33 and may be provided with suitable piston rings 12 to provide a seal between these parts.

The cylindrical portion 16 is adapted to reciprocate within the reduced bore 54 of the cylinder 33 and is in turn provided with a pair of oil packing rings I4 which generally provide a seal between the piston head and the bore 54 and also serve to reciprocate the same. The upper portion 66 of the piston 16 may be formed with the vertical opening I6 and the raised stud portion I6 therein. A comparatively heavy compression spring is adapted to be positioned in the opening 16 between the lower wall thereof and the lower wall of a socket 82 formed in the lower wall of the cylinder cap 30. I also provide a piston snubber block 84 positioned in a vertical opening 86 in the cylinder cap 30 between the head of the bolt 32' and the top of the stud 18.

With the construction of the reciprocating piston and the cylinder as thus far described, it

.from the cover portion justing screw I24.

downwardly against the top 26a of the tool holder 26 with considerable force.

The means for raising the piston to the operative position discussed will now be described. The neck portion 69 of the piston I0 is formed with the cylindrical adapted to be engaged by the upper cammed surface 90 of the fingers 92 at the end of the operating lever 94. The lever 94 has a hub porshoulder 88. This is tion 96 provided with abore 98 through which a pivot pin I69 is positioned. The pivot pin- !66 may be formed with a cylindrical headfIIJ2 adapted to be journalled in a socket I03 in the housing I4 and a reduced portion I64, adapted to be journalled in a boss. I05 extending inwardly housing I6. A nut member I08 secured to a threaded portion III! on the pin I00 securely,

ms of the flexible drive spaced side walls 94a between which a roller II2,

is adapted to be mounted upon a suitable pivot H4. In order to reduce friction to a minimum,

a roller II2 has been provided with a ball bearing mounting upon the pin. II 4. Means for 'reciprocating the lever 94 in an up and down di-j rection are providedin the form of a cam -II6;'

The cam I I6 is formed with the rise track-H8 and the drop track I26 which, as will be noted, provides a gradual rising of the lever andjan abrupt drop of the same. Thus, when the cam is rotated in the direction of the arrow asshown in Fig. 3, the lever 94 will raise the piston III to the position shown in the drawings, and as thecam passes from the high point, the cam-will not.

interfere with the sudden drop of' the roller H2 or the drop of the piston III. In'this'manner' the eifective blow struck by the piston will re? ceive its entire momentum from the compression spring 86 and thecompression of the air in the chamber of the cylinder above the piston as previously explained. In order to provide a shock absorber or snubber action for the lever 94, I prov1de the compression spring I22 positioned between a portion of the lever 94 and the top of a washer I23 secured on an adjusting bolt I24. The adjusting bolt I24 may be screw-threadedly mounted in a block I25 that has been cast integral with the housing I4. I provide a spring clip member I21 secured in position by oneof the bolts I4a of the housing I4. that normally holds the head I28 of the. ad-

Thus, when it is desired to increase or decrease the tension on the spring I22, this action may be eifected by turning the head I28 by means of a hexagonally headed wrench that is screw head.

As previouslym entioned, the flexible drive:

housing I6 is secured to the side of the housing I4 and is formed with the cover plate portion I66 that engages about the opening I32 in the housing I4.- may be rigidly secured together These housings by means oithe placed'in the socket 'I29'in the periphery ofthe-side bolt members I4a which pass through suitable openings inboth housings. In order to provide liquid proof seals, suitable gasketsare provided about the openings. Means for rotating the cam I I6 may include the shaft I34 fixedly secured to the cam 'I I6 and mounted in'the flexible drive housing I6 between suitable needle bearings I36 adjacent both ends of the shaft. A suitable spacer I38 may be provided between the sets of bearings. The cam shaft I34 is formed with an axial opening I40 adapted to receive the tip I42 of a flexible drive shaft I44. The housing I46 may be connected in the end of the housing I4 in the well known manner, and the flexible drive shaft I44 may engage the splined driving tip l42 of the shaft I34 and in this way the flexible shaft is connected to the cam shaft'to drive the same.

From the foregoing description, it will beuapparent to those skilled in the art that a comparatively hammer construction has been provided. It will also be obvious that by the simple expedient of removing the handle I!) and the" cylinder cap 3!! the cylinder and its associated parts maybe withdrawn for repair or replacement. By reason of the construction of the cam, it can be seen that the lever 94 is forced upwardly and then to effect the work stroke the cam, by reason of its shape is quickly gotten out of the way of the descending roller 2, thus providing in this construction highly efficient means for a work hammer construction. By reason of the cushioning at the bottom of the piston stroke, itis obvious that all of the parts will Wearlonger because there is no harsh pounding as is found in many of the hammers at present in use. The cushioning of the lever in its descent is also a desirable feature which adds greatly to the life and satisfactory operation of applicant's construction. 1

While I have illustrated and described one embodiment of my invention, it will be obvious to those skilled in the art. that changes and modifications may be made in the details shown, and I do not wish to limit myself in any particular; rather what I desire to secure and protect by Letters Patentof the United States is:

1. A mechanically driven power hammer including in combination, a housing havinga cylinder, a piston reciprocably mounted in said cylinder, a work engaging tool one end of which is removably extended into one end of the cylinder in a position to be engagedby one end of said piston, a compression spring disposed in the cylinder between the other end thereof and the other end of the piston, and piston operating means including a lever extending transversely of the longitudinal axis of said piston, engaging the piston at one end, and'pivoted to the housing at its other endfor swinging movement in the common plane of the lever and piston, a cam rotatably mounted in said housing intermediate the ends of the lever, on the opposite side of the lever from said compression spring and adapted to move said lever against the compression of said spring, and. a flexible shaft drive for said cam.

2. A mechanically driven power hammer as definedin claim 1, wherein the piston has a reduced waist region defined between spaced shoulders, and wherein the piston engaging end of the lever is in the form of a fork embracing said reduced waist region and engageable against said shoulders.

3. A mechanically driven power hammer insimple, yet highly efficient powercluding in combination, a housing having a cylinder, a piston reciprocably mounted in said cylinder, a work engaging tool one end of which is removably extended into one end of the cyl-,

inder in a position to be engaged by one end of said piston, a compression spring disposed in the cylinder between the other end thereof and the other end of the piston, and piston operating. means including a lever extending transversely of the longitudinal axis of said piston, engaging the piston at one end, and pivoted to the housing at its other end for swinging movement in the common plane of the lever and piston, a cam rotatably mounted insaid housing intermediate the ends of the lever, on the opposite side of the lever from said compression spring and adapted to move said lever so as to move said piston against the compression of said spring and compress the air between said piston and'an end of the cylinder, and a flexible shaft drive for said cam.

4. A mechanically driven power hammer including in combination, a housing having a cylinder, a piston reciprocably mounted in said cylinder, a work engaging tool one endof which is removably extended into one end of the cylinder in a position to be engaged by one end of said piston, a compression spring disposed in the cylinder between the other end thereof and the other end of the piston, and piston operating means including a lever extending transversely of the longitudinal axis of saidpiston, engaging the piston at one end, and pivoted to the housing at its other endfor swinging movement in the. common plane of the lever and piston, a cam for moving the lever against the compression of said spring and a recoil spring for cushioning the lever on the working stroke of the piston, said cam and recoil spring being both disposed intermediate the ends of the lever on the opposite side thereof from said compression spring, and a flexible shaft drive for said cam.

5. In a mechanical power hammer the combination of a housing having a vertical bore through one side thereof, a removable cylinder mounted in said bore, said cylinder having a shoulder adjacent its lower end engaging the bottom of said housing and a cap secured thereto at its top and engaging the top of said housing whereby said cylinder is held in fixed position therein, a reciprocable piston mounted in said cylinder, a work tool adapted to be extended from the lower end of said cylinder, a compression spring in said cylinder positioned between said cap and the upper end of said piston, a pivoted arm for raising said piston and a rotatable cam for operating said arm, said cam driven by means of a flexible drive shaft.

6. In a mechanical power hammer the combination of I a housing having a vertical bore through one side thereof, a removable cylinder mounted in said bore, said cylinder having a shoulder adjacent its lower end engaging the bottom of said housing, and a cap secured thereto at its top and engaging the top of said housing whereby said cylinder is held in fixed position therein, a reciprocable piston mounted in said cylinder, a work tool adapted to be extended from the lower end of said cylinder, a compression spring in said cylinder positioned between said cap and the upper end of said piston, a pivoted arm for raising said piston and a rotatable cam for operating said arm, a shaft for said cam extending at right angles from said housing, a drive nut secured thereto, a flexible shaft having a tip engaging said drive nut and a remotely placed source of power for said shaft.

7. In a mechanical power hammer the combination of a housing, a removable cylinder mounted in said housing, a reciprocable piston mounted in said cylinder, a work tool adapted to be extended from one end of said cylinder, a cap in the other end of said cylinder, a compression spring in said cylinder positionedbetween said cap and the upper end of said piston, a flexible bumper member in said cylinder above said piston, a pivoted arm for raising said piston to compress said spring, a revolving cam for raising said arm, a bumper spring below said arm and means including a flexible drive shaft for operating said cam.

8. A mechanically driven power hammer including in combination, a housing having a cylinder, a piston reciprocably mounted in said cylinder, a work engaging tool one 'end of which is removably extended into one end of the cylinder in a position to be engaged by one end of said piston, a compression spring disposed in the cylinder between the other end thereof and the other end of the piston, and piston operating means including a lever extending transversely of the longitudinal axis of said piston, engaging the piston at one end, and pivoted to the housing at its other end for swinging movement in the common plane of the lever and piston, a cam rotatably mounted in said housing intermediate the ends of the lever, on the opposite side of the lever from said compression spring and adapted to move said lever against the compression of said spring, and resilient bumper means in the cylinder between the tool engaging end of the piston and the adjacent end of the cylinder, and a flexible shaft drive for said cam.

9. A power hammer comprising a housing, said housing having a vertical bore adjacent one side thereof, a cylinder mounted in said bore, said cylinder having a flange engaging the lower wall of said housing, a cap for said cylinder engaging the upper wall of said housing and thereby locking said cylinder in position in said housing, a piston in said cylinder, means for raising said piston comprising a lever mounted in said housing, a cam for operating said lever, a flexible drive connected to said cam and spring means positioned between said cap and the upper end of said piston for lowering said piston in a hammer thrust, said piston provided with piston rings whereby air is compressed upon the upward stroke of said piston.

10. A power hammer comprising a housing, said housing having a vertical bore adjacent one side thereof, a cylinder mounted in said bore, said cylinder having a flange engaging the lower wall of said housing, a cap screw-threadedly mounted in the-upper end of said cylinder en-' gaging the upper wall of said housing and thereby locking said cylinder in position in said housing, a piston in said cylinder, means for raising,

said piston comprising a lever mounted in said housing, a recoil spring below said lever, a cam in said housing for raising said lever, a drive shaft for said cam, a flexible drive connected thereto and compression spring means positioned between saidcap and the upper end of said piston for lowering said piston in a hammer thrust, a resilient bumper positioned between the coils of said second spring, said piston provided with piston rings whereby air is compressed upon the upward stroke of said piston.

1 A power hammer comprising a housing,

said housing having a vertical bore adjacent one,

side thereof, a cylinder mounted in said bore,

said cylinder having a flange engaging the lowerwall of said housing, a cap screw-threadedly mounted in the upper end of said cylinder engaging the upper Wall of said housing and thereby locking said cylinder in position in said housing, a piston in said cylinder, means for raising said piston comprising a lever mounted in said housing, a recoil spring below said lever, means for adjusting the tension on said spring, a cam in said housing for raising said lever, a drive shaft for said cam, a flexible drive connected thereto and compression spring means positioned between said cap and the upper, end of said piston for lowering said piston in a hammer thrust, a resilient bumper positioned between the coils of said second spring, said piston provided with piston rings whereby air is compressed upon the upward stroke of said piston.

12. In a mechanical power hammer the combination of a housing having a vertical bore through one side thereof, a removable cylinder mounted in said bore, said cylinder having a shoulder adjacent its lower end engaging the bottom of said housing and a cap secured thereto at its top and engaging the top of said housing whereby said cylinder is held in fixed position therein, a reciprocable piston mounted in said cylinder, a work tool adapted to be extended from the lower end of said cylinder, a compression spring in said cylinder positioned between said cap and the upper end of said piston, a

rubber bumper on both sides of said piston for 

